Recent reports to the CDC have documented ten cases of septic shock, including seven deaths, due to red blood cell (rbc) transfusions contaminated with Yersinia enterocolitica. These incidents were associated with units older than 25 days. The possibility of reducing the dating period to 25 days for stored rbc was considered as a potential means for reducing the risk of transfusion of a contaminated unit. To obtain information on the expected impact on the blood supply of such a change, a questionnaire on blood storage patterns and rbc contamination by Y. enterocolitica was distributed to all registered blood establishments in March, 1991. Data were obtained from approximately 1600 blood establishments including virtually all the major organizations engaged in blood collection and distribution. Combining all centers and all dating periods for stored units, approximately 20% of the national inventory of rbc was found to exceed 28 days of storage, suggesting a major dislocation if the dating period were to be reduced. Only a single new case of adverse reaction to Y. enterocolitica was identified, indicating the adequacy of prior reporting. These data contributed to a decision by the Blood Products Advisory Committee, in May, 1991, not to recommend reduced dating for refrigerator stored rbc.